1. Field of the Invention
The present relates to a linear guide apparatus having a large impact resistance.
2. Description of the Art
A linear guide apparatus includes an axially extending guide rail having rolling body rolling grooves formed in side surfaces thereof and a slider movably fitted on the guide rail and having rolling body rolling grooves formed in inner surfaces of side walls thereof so that the rolling body rolling grooves of the slider respectively oppose the rolling body rolling grooves of the guide rail. The slider is smoothly movable in an axial direction through rolling of a plurality of rolling bodies rollably inserted between the opposed rolling body rolling grooves of the guide rail and the slider. Linear guide apparatus of this type are known in the art. For example, a linear guide apparatus including a guide rail having a square cross section, a slider having an inverted U-shaped cross section and straddling the guide rail, and rollers used as the rolling bodies is disclosed in Japanese Utility Model Laid-Open Publication No. 64-35220. A linear guide apparatus including a similar guide rail having a square cross section, a slider having an inverted U-shaped cross section and straddling the guide rail, and balls used as the rolling bodies is disclosed in Japanese Utility Model Laid-Open No. 63-171722. A linear guide apparatus including a guide rail having a square cross section and a slider fitted into an inside of the guide rail is disclosed in Japanese Utility Model Laid-Open No. 63-121817.
Such linear guide apparatuses are used in various applications as linear guide bearings and, for example, in the case of machine tools, as a guide and the like of a carriage of a lathe.
However, the linear guide apparatus is not necessarily loaded with a load of a certain limit. For example, when a carriage of the lathe collides with a chuck or the like, a large impulsive load will be generated. In the case where such an impulsive load is applied, since the total contact area of the contact portions between the rolling bodies and the groove surfaces of the rolling body rolling grooves of a linear guide apparatus is small, a the per unit contact area becomes very large. As a result, the contact portions at which the rolling body is in contact with the groove surfaces of the rolling body rolling grooves of the guide rail and the slider will be plastically deformed and there is a fear that harmful impressions will be made in the surface of the rolling body and in the groove surfaces.
In the prior art, when it is presumed that a harmful impulsive load will be applied to the linear guide apparatus, in order to bear such an abnormally large load, the number of sliders is increased, or a linear guide apparatus having a large load capacity is used as a countermeasure. Accordingly, a problem is involved in that such measures are uneconomical in view of the space required and the price of the large linear guide apparatus.